1. Field of the Invention
This invention relates to a system which enables a three-dimensional analysis, through physical measurements, that detects the shape of a fracture, an underground water fluidizing state containing geothermal water (hereinafter, simply underground water fluidizing), and its distribution state adjacent to boreholes dug in the ground.
2. Discussion of the Background
Formally, for this kind of geophysical technology in general, there exists; a method which measures specific resistance of the ground by utilizing electromagnetic phenomena, a method which measures a transmission wave or a reflection wave by emitting an ultrasonic wave or an elastic wave, and a method which investigates the underground rock density by measuring natural .gamma. rays in the ground, or by measuring scattering of .gamma. rays from an artificial radiation source. A method which is called geotomography, is performed to search underground dislocation states by data gathering and treating of these measurement results. Furthermore, in recent times, in addition to this, a three-dimensional approach is being tried by effectively using available boreholes.
However, these conventional underground search methods have difficulties in accurately detecting the shape of a fracture in the earth crust, the underground water fluidization state, and its distribution, to accurately grasp the existence or the shape of an underground water fluidization layer in rock fissures, a hydrocarbon or oil layer, probably due to the roughness of the sampled data. The existence of the geothermal water layer can be estimated by the existence of a gushing steam. A chemical substance such as potassium iodide, used as a fluidization index, is injected into a gushing borehole, under a precise control on the predetermined time interval and the concentration. By sampling the chemical substance from a borehole drilled at another place or from another gushing borehole, and by measuring its concentration and sampling time, the shape of a fracture in the earth crust, geothermal water fluidization state, and its distribution state, are estimated. However, the numerical value of the chemical substance would be known only after the sampling, and the change in the concentration can be considerably subtle.
Furthermore, in this search involving the injection of a chemical substance, only the end points of the underground water fluidization can be estimated, and the passage of fluidization can not accurately be grasped.